docs: def _open_config_files(self, command_line_args):
          """Tries to parse config file path(s) from within command_line_args.
          Returns a list of opened config files, including files specified on the
          commandline as well as any default_config_files specified in the
          constructor that are present on disk.
  
          Args:
              command_line_args: List of all args (already split on spaces)
          """
          # open any default config files
          config_files = [open(f) for files in map(glob.glob, map(os.path.expanduser, self._default_config_files))
                          for f in files]
  
          # list actions with is_config_file_arg=True. Its possible there is more
          # than one such arg.
          user_config_file_arg_actions = [
              a for a in self._actions if getattr(a, "is_config_file_arg", False)]
  
          if not user_config_file_arg_actions:
              return config_files
  
          for action in user_config_file_arg_actions:
              # try to parse out the config file path by using a clean new
              # ArgumentParser that only knows this one arg/action.
              arg_parser = argparse.ArgumentParser(
                  prefix_chars=self.prefix_chars,
                  add_help=False)
  
              arg_parser._add_action(action)
  
              # make parser not exit on error by replacing its error method.
              # Otherwise it sys.exits(..) if, for example, config file
              # is_required=True and user doesn't provide it.
              def error_method(self, message):
                  pass
              arg_parser.error = types.MethodType(error_method, arg_parser)
  
              # check whether the user provided a value
              parsed_arg = arg_parser.parse_known_args(args=command_line_args)
              if not parsed_arg:
                  continue
              namespace, _ = parsed_arg
              user_config_file = getattr(namespace, action.dest, None)
  
              if not user_config_file:
                  continue
              # validate the user-provided config file path
              user_config_file = os.path.expanduser(user_config_file)
              if not os.path.isfile(user_config_file):
                  self.error('File not found: %s' % user_config_file)
  
              config_files += [open(user_config_file)]
  
          return config_files